As is known, virtually all facilities which utilize electric power receive such power from a utility company. Typically, such utility companies have an excellent record of providing uninterrupted or infrequently interrupted power at proper voltage levels and line frequency. However, due to the increasing demands for power, power outages have become more frequent. While such outages usually last for a only a short duration, an extended power outage may cause more than simple aggravation for customers of the utility company. By way of example, for a residential customer, any power outage renders a home owner's sump pump inoperable. If a power outage occurs during a rain storm, it is quite possible that the failure of the sump pump to operate will result in the flooding of a home owner's basement.
In order to overcome these occasional disruptions in service, various customers, including home owners, have equipped their facilities with stand-by power systems. These stand-by power systems include internal combustion engines which drive electrical generators. If the commercial power from the utility company fails, the internal combustion engine is automatically started causing the electrical generator to generate power. When the power generated by the generator reaches the voltage and frequency desired by the customer, a manually operated transfer switch transfers the load imposed by the customer from the commercial power lines to the generator.
Typically, the transfer mechanism incorporates a switch which isolates the power supplied by the utility company and the generator. In a residential application, a home owner manually flips a switch between the utility source and the generator in order to provide power to the electrical system of the home. However, due to a potential time delay before the home owner can flip the switch, a significant amount of damage may be sustained by a home owner before power is supplied to the electrical system of the home. For example, an extended power outage may result in foodstuffs spoiling within a refrigerator or melting within a freezer. Therefore, it is highly desirable to provide a transfer mechanism which automatically transfers power from the utility company to the generator whenever the generator is activated.
Further, prior art transfer mechanisms require a home owner to transfer the entire electrical system of the home onto the generator. Such an arrangement does not allow a home owner the ability to decide which circuits of a home's electrical system to be powered. As such, it is also desirable to provide a transfer mechanism which allows various branch circuits of a home to be brought on line separately, rather than at once, to allow for loads with large starting requirements to be brought up to speed before bringing the other circuit branches of the home on line thereby insuring that adequate power is provided by the generator to start such loads.
Therefore, it is a primary object and feature of the present invention to provide a transfer mechanism for transferring power between a utility source and a stand-by generator.
It is a further object and feature of the present invention to provide a transfer mechanism which automatically transfers power from the utility source to the generator in response to a power outage.
It is a still further object and feature of the present invention to provide a transfer mechanism for transferring power between a utility source and a generator which allows for the bringing of individual circuit branches of a home electrical system on line separately.
It is a still further object and feature of the present invention to provide a transfer mechanism which is simple to install and inexpensive to manufacture.